Refactor usage pages with shortcodes, convert HTML to Markdown

Add usage-lead and usage-feature shortcodes to encapsulate the
alternating two-column layout, then migrate all ten usage pages
(cio, sysadmin, freelance, geek, devops — EN and FR) from raw
HTML files to plain Markdown using those shortcodes.

content/use-happyDomain/geek.en.md

@@ -0,0 +1,58 @@
++++
+title = "happyDomain for Enthusiasts"
+description = "Take control of your domain names with a powerful, open-source interface. happyDomain makes DNS management fun and accessible for hobbyists and tech enthusiasts."
+layout = "usage"
++++
+
+{{< usage-lead >}}
+An interface to <span class="text-hilight">keep your independence</span> on the web.
+{{< /usage-lead >}}
+
+{{< usage-feature
+  title="Discover a simple and clear interface."
+  image="/img/screenshots/domain-abstract.webp"
+  alt="Liste des domaines, regroupés astucieusement par client"
+>}}
+Whatever the host of your zones, happy<span class="fw-bold">Domain</span> displays them in a clear way to limit errors.
+
+By installing happy<span class="fw-bold">Domain</span> next to your Bind or PowerDNS, enjoy the interface without changing your configuration.
+<span class="text-muted">(coming soon)</span>
+{{< /usage-feature >}}
+
+{{< usage-feature
+  title="Self-hosting made easy."
+  image="/img/screenshots/domain-abstract.webp"
+  alt="Liste des domaines, regroupés astucieusement par client"
+  flip="true"
+  bg="green"
+>}}
+happy<span class="fw-bold">Domain</span> allows you with the same interface to manage your DNS zone with a third party provider, or to manage your own DNS servers.
+
+Don't be afraid to edit a zone text file, we take care of it!
+
+Our solution doesn't need a lot of resources and can be used on a Raspberry Pi. Or even be launched only when needed.
+{{< /usage-feature >}}
+
+{{< usage-feature
+  title="Meet all your needs in all simplicity."
+  image="/img/screenshots/domain-services.webp"
+  alt="Liste des domaines, regroupés astucieusement par client"
+>}}
+A new service? An urgent fix? happy<span class="fw-bold">Domain</span> uses simple terminology to stay focused on the expected result.
+
+We are committed to providing the latest in DNS registration and services.
+{{< /usage-feature >}}
+
+{{< usage-feature
+  title="Manage easily, even special zones."
+  image="/img/screenshots/service-caa.webp"
+  alt="Liste des domaines, regroupés astucieusement par client"
+  flip="true"
+  bg="plum"
+  coming_soon="true"
+>}}
+Looking for an interface that displays reverse IPv4/IPv6 zones in a human way?
+Or a <a href="https://en.wikipedia.org/wiki/DNSBL">Real-time Blockhole List (DNSBL)</a> zone? Or a DNS <a href="https://www.dnsrpz.info/">Response Policy Zones</a> (DNS-RPZ)?
+
+happy<span class="fw-bold">Domain</span> understands them and allows you to manage them unequivocally.
+{{< /usage-feature >}}